A strong demand exists for the introduction of electric vehicles (EV) and hybrid electric vehicles (HEV), fuel cell vehicles (FCV) as well as batteries for driving vehicle motors. The use of secondary batteries, which can be recharged repeatedly, as batteries for driving said motors have been proposed. Because EVs, HEVs, and FCVs require high-output and high-energy density, it is difficult to meet these requirements using a single large-size battery. Thus, it is common practice to use an assembled battery comprising multiple batteries connected in series. Thin laminate battery batteries have been suggested as a suitable assembled battery.
In general, a positive electrode and a negative electrode for the battery in question can be fabricated by applying a coating solution containing a positive electrode active material or a negative electrode active material onto a suitable collector. While various kinds of roller coaters can be employed, it has been found that performance quality of the resulting battery can suboptimal due to uneven layer coating. This can manifest as uneven battery heat dissipation which, in turn, may result in partial degradation of the battery. In addition, a battery with localized variations in electrode thickness varies locally is prone to resonate as vibrations are applied to the battery; resulting in cracking and breaking of the base material. This becomes particularly problematic when long battery life is desired or required. For instance in automotive vehicular applications, the expected battery life for the associated vehicle battery may be 10 years or longer.
In order to reduce unevenness of the electrode coating, it has been proposed to control the viscosity of the coating solution. Even so, when a conventional coater is used to apply a liquid containing the electrode active constituent materials, it is difficult to form a film with uniformity above a certain level. For example, when coating is carried out intermittently, the electrode constituent materials accumulate in localized regions resulting in local regions of greater thickness.
Additionally, when high battery output is required, the thickness of the battery may have to be reduced in order to connect many individual batteries in series. However, it is difficult to fabricate an extremely thin battery using a conventional coater.